Integrated circuit (“IC”) die or “die” are typically mounted in or on a package in order to form a semiconductor device, also referred to as a “semiconductor device package”, a “semiconductor chip package”, a “semiconductor package” or an “IC device package”. Mounting of an IC die to a package facilitates subsequent attachment of the resulting semiconductor device to a printed circuit board (“PCB”) or other component of an electronic assembly. Typical non-wirebonded two-terminal surface-mount discrete power semiconductor devices consist of a lead frame on which the bottom side of a semiconductor die or chip is mounted, and either a one-piece or a two-piece clip that makes a connection to the top side of a semiconductor die. FIG. 11 is a side view of a semiconductor package 1100 that uses a one-piece clip 1102 to connect to the semiconductor die 1104, under the prior art. FIG. 12 is a side view of a semiconductor package 1200 that includes a two-piece clip 1202A/1202B for connecting to the semiconductor die 1204, under the prior art. FIG. 13 is a side view of another semiconductor package 1300 that uses a two-piece clip 1302A/1302B to connect to the semiconductor die 1304, under the prior art.
The semiconductor package that uses the two-piece clip has an advantage in that the joint between the top and bottom pieces that form the clip allows the clip to “float” on the semiconductor die. The clip floating means the joint between the pieces of the clip acts as a lever point that enables adjustments to the position of the clip relative to the top side of the semiconductor die, thereby ensuring proper connection of the clip to the top side.
However, the joint between the top and bottom pieces of the two-piece clip increases the difficulty and cost of manufacturing the semiconductor package and reduces the units per hour (“UPH”) rate in assembly. Further, the joint between the top and bottom pieces of the clip necessitates an extra solder joint, and the solder joint is a point where the connection to the semiconductor die may be lost as a result of poor process control in the solder dispensing or reflow operations. Additionally, centering of the clip on the top side of the semiconductor die becomes constrained by the process control capability over both the clip and the semiconductor die.
The semiconductor package that uses the one-piece clip has an advantage in that elimination of the joint between the top and bottom pieces that form the two-piece clip reduces the cost of manufacturing, increases the UPH rate, and reduces the chances of having an open circuit in the path to the semiconductor die top side. Use of the one-piece clip realizes another advantage in that x-dimension control over centering of the clip on the semiconductor die top side depends primarily on placement control of the semiconductor die on the lead frame.
However, use of the one-piece clip can also introduce problems in manufacturing in the absence of adequate process control to ensure that the distance between the top side of the semiconductor die and the contact portion of the clip that contacts the top side does not exceed the maximum distance across which solder can make the specified connection. There exists a possibility that, when the manufacturing process control allows this maximum distance to become excessive, the solder will not wet to the clip and consequently only a mechanical compression contact is formed between the contact portion of the clip and the top side. The mechanical compression contact is unreliable because it can subsequently result in intermittent electrical contact with the semiconductor die top side or an open electrical circuit. Therefore, use of the one-piece clip can necessitate higher manufacturing tolerances in the areas of bow angle and skew on the clip during manufacture of the semiconductor packages.
In the drawings, the same reference numbers identify identical or substantially similar elements or acts.